Oil circuit interrupter having improved stack insulating washer structure

ABSTRACT

An arc interrupting device for use in an oil-type circuit interrupter comprises a hollow tubular insulated external structure with annular oil pockets on the interior surface thereof and oil flow nozzles through the wall thereof. The external structure houses an electrically conductive stationary contact assembly. A cylindrical insulated internal structure with annular oil pockets on the exterior surface thereof is concentrically disposed inside the external structure. An electrically conductive hollow cylindrical bayonet contact is movable in the annular space between the external and internal structures. During withdrawal of the bayonet, the arc formed between it and the stationary contact is constricted in the narrow annular space and is thereby more readily cooled and extinguished. In another embodiment, the bayonet contact and the space which accommodates it both have a C-shaped cross-sectional configuration.

United States Patent [72] Inventors Herbert M. Pflanz Roslindale; JosephM. Ramrath, Mattapan, both of, Mass. [211 App]. No. 880,667 [22] FiledNov. 28, 1969 [45] Patented Aug. 31,1971 [73] Assignee Allis ChalmersManufacturing Company Milwaukee, Wis.

[54] OIL CIRCUIT INTERRUPTER HAVING IMPROVED STACK INSULATING WASHERSTRUCTURE 5 Claims, 3 Drawing Figs.

[52] U.S.Cl ZOO/150B [51] lnt.Cl ...H0lh 33/68 [50] Field of SearchZOO/149.1, 149,15OB,150'D,150G

[56] References Cited UNITED STATES PATENTS 2,1 18,355 5/1938 Matthews200/1 49 A 2,130,999 9/1938 Petermichl. 200/149 A 2,192,045 2/1940 Linde200/149 A 8/1941 Baker 9/1942 Rawlins t.

200/ l 50 G ZOO/149 A Primary Examiner-Robert S. Macon AtmmeysThomas F.Kirby, Lee H. Kaiser and Robert B.

Benson ABSTRACT: An arc interrupting device for use in an oil-type vcircuit interrupter comprises a hollow tubular insulated exterbetween itand the stationary contact is constricted in the narrow annular spaceand is thereby more readily cooled and extinguished.

In another embodiment, the bayonet contact and the space whichaccommodates it both have a C-shaped cross-sectional configuration.

PATENTED AUB31 1971 3.602671- sum 1 [1F PATENTED A0831 IS?! SHEET 2 OF 2El m paw. #9

JQM R OIL CIRCUIT IN TERRUPTER HAVING IMPROVED STACK INSULATING WASHERSTRUCTURE CROSS-REFERENCE TO RELATED PATENT APPLICATIONS The presentapplication discloses a sliding contact which is disclosed and claimedin US. application Ser. No. 785,227, filed Dec. 19, 1968 for SlidingContact by Joseph M. Ramrath and assigned to the same assignee as thepresent application.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates generally to oil-type electric circuit interrupters and,particularly, to are interrupting devices employed therein.

2. Description of the Prior Art A typical oil-type circuit interruptercomprises an oil filled tank in which one or more arc interruptingdevices are disposed and submerged in oil. Each device, for example,.

comprises a housing made of insulating material in which a stationarycontact is located. A movable bayonet-type contact is adapted tobeinserted into the housing to engage the sta tionary contact. Arcingwhich occurs in the housing upon contact separation is quenched by oilflow through the housing. In some interrupters the bayonet is relativelylarge, i.e., on the order of 2 inches in diameter in order to carryheavy continuous currents. However, such large diameter bayonetsgenerally reduce the interrupting performance of the interruptingdevice. This is because the are time constant is a measure of thethermal recovery of an arc plasma column and is proportional to the arcradius squared. The problem is overcome to some extent by using smalldiameter bayonets which are shunted by contact arrangements havinglarger cross-sectional area but this solution is costly, space consumingand requires extra components. It is known that, if the diameter of thearc can be kept relatively small, then it can be cooled more rapidly andfaster dielectric recovery of the arc path can be obtained. For example,U.S. Pat. No. 3,140,374 issuedto F. H. Cole shows a solid bayonetcontact having an insulated tip which is of smaller diameter than thebayonet. Thus when the bayonet is withdrawn from the interrupter device,the arc is confined to a narrower space than would otherwise be the caseand is more readily quenched. US. Pat. Nos. 2,591,950 and 2,671,144 showother solutions to this problem. However, it is desirable to provideimproved interrupters wherein the arc is completely constricted butwherein large current carrying components can still be employed.

SUMMARY OF THE INVENTION In accordance with the present invention thereis provided an arc interrupting device for submersion in oil whichcomprises a hollow tubular external structure made of insulatingmaterial and preferably having annular oil pockets on the interiorsurface of the wall and oil flow nozzles through its wall. A stationarycontact assembly is associated with one end of the structure. Aninternal structure made of insulating material and preferably havingannular oil pockets on its exterior surface is concentrically disposedinside the external structure and cooperates therewith to define anarrow annular space. A relatively large diameter hollow movable bayonetcontact for cooperation with the stationary contact is adapted to beinserted in and withdrawn from the space, surrounding the internalstructure in the process. The arc which occurs upon withdrawal of thebayonet contact is drawn into the narrow space wherein its diameter isnecessarily reduced and it is easily cooled by vaporized and dissociatedgas from the oil until interruption occurs. In another embodiment of theinvention, the space and bayonet contact have substantially C-shapedcross sections, rather than annular cross sections.

OBJECTS OF THE INVENTION It is an object of the present invention toprovide improved arc interrupting devices for electric circuit breakers.

Another object is to provide devices of the aforesaid character whichemploy movable bayonet contacts and have improved means for constrictingthe are formed as the bayonet contact is withdrawn from the device.

Another object is to provide devices of the aforesaid character whereinthe arc is constricted substantially along its entire length. g 7

Another object is to provide devices of the aforesaid character whereinthe constricted arc is exposed to an increased number of oil turbulencepockets along its entire length. i

Other objects and advantages of the invention will hereinafter appear.

DESCRIPTION OF. THE DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENTSReferring to FIGS. 1 and 2 of the drawing, an arc interrupting device 8in accordance with the invention is adapted to be disposed inside thetank of a high voltage-high current oil circuit breaker and iscompletely submerged in oil. The device is mounted on an electricallyconductive contact member or casting 10 which is understood to beconnectable to one side of the line in an electric circuit which acircuit interrupter controls. Casting 10 is understood to be circular inshape and is provided with'screw threads 12 on its outer periphery bymeans of which an external interrupter structure 14 of the interruptingdevice is supported on the casting. Casting 10 is further provided witha central opening 16 by means of which an internal interrupter structure18 is supported on the cast- External structure 14 comprises a hollowcylindrical outer shell 20 which is made of insulating material and hasa plurality of nozzle openings 21 through the wall thereof toaccommodate oil flow. Shell 20 is provided with cylindrical, internallythreaded inserts or collars 22 and 24 at its top and bottom ends,respectively..Top insert 22 engages the threads l2 on casting 10. Bottominsert 24 is adapted to engage a closure member or plate 26 which iscircular in shape and is provided with screw threads 30 on its outerperiphery and with a central opening 32.

External structure 14 has a stationary contact assembly 34 near itsupper end, which assembly is of a type completely described in US.patent application Ser. No; 785,227 hereinbefore referred to. Assembly34 comprises an electrically conductive circular retainer 36 having acentral opening 38 therein. Retainer 36 carries a plurality ofelectrically conductive contact fingers40 which are radially arrangedaround opening 38 and biased inwardly by springs 42. A plurality ofretaining rings 44, 46 and 48 made of insulating material maintain thecontact fingers 40 and the springs 42 in proper position. Stationarycontact assembly 34 is held in position by entrapment of its retainer 36between contact casting 1 0 and a shoulder 50 formed in shell 20 ofexternal structure 14. An electrically conductive path exists betweeneach contact finger 40, retainer 36 and contact casting 10.

54 have the same outside diameter but the diameterof a cen-, tralopening 56 in each washer 52 is smaller than that of a cen-' tralopening 58 ineach washer 54. Consequently, disposition of one or morewashers 54 between each pair of washers 52 provides a series of annularoil pockets 60 along the interior of external structure 14. The washers54 adjacent the oil nozzles 21 are provided with openings 62 whichaccommodate oil flOW. i

Internal interrupter structure 18 comprises an elongated solidcylindrical insulating support member or rod 64 having a tapered head 65which engages opening 16 in contact casting 10. The lower end of rod 64is provided with screw threads 66 on. which a nut 68 made ofinsulatingmaterial is disposed. A plurality of washers 70 and 72 made ofinsulating material are stacked on rod 64 and held in place byentrapment between nut 68 and a cylindrical sleeve 74 made of insulatingmaterial and located at the top of the'rod. The washers 70 and 72 havecentral openings 76 which are of the same diameter but the outsidediameter of each washer 70 is greater than that of each washer 72.Consequently, disposition of one or more washers 72 between each pair ofwashers 70 provides a series of annular oil pockets 78 along theexterior of internal structure 18. 7 The external structure 14 andinternal structure 18 define a cylindrical space 80 into and out ofwhich a hollow, cylindrical electrically conductive bayonet contact 82is axially movable. It is to be 54 understood that contact 82 iselectrically connectable to the other side of a line in a circuit whichthe circuit interrupter controls. Clearance between the inside andoutside surfaces of bayonet contact 82 and the washers 70 and 52 ispreferably at a minimum consistent with good engineering practice. Inpractice, for example, bayonet contact 82 hasan outside diameter on theorder of 3% inches and has a crosssectional area suitable for carryinghigh continuous current and higher momentary currents. A large bayonetdiameter provides a proportionately large circumference and permits manycontact fingers such as 40 to be in engagement therewith and thisreduces overall contact resistance.

An arc interrupting device according to FIGS. 1 and 2 operates asfollows. Assume first that bayonet contact 82 is in contact closedposition as shown in the drawing wherein its tip is in electricalcontact with the contact fingers 40 of stationary contact 34. Furtherassume that there is current flow through the contacts. To open thecontacts, bayonet contact 82 is moved downwardly by suitable means (notshown) and an arc is drawn between the tip of contact 82 and the contactfingers 40. As downward travel of contact 82 continues, the arcterminals transfer from the contact fingers 40 to the lower inner edgeof retainer 36 of stationary contact 34 and the arc is completelyconfined or contained in the annular space vacated by bayonet contact 82between external structure 14 and internal structure 18. The are beingso constricted has a smaller diameter along its entire length than wouldotherwise be the case and is effectively cooled by vaporized anddissociated gases formed from the oil until interruption occurs. If thearc being interrupted is an alternating current arc, more rapid coolingof the arc occurs by the time the current zero point is reached andfaster dielectric recovery along the arc path is obtained. Oil flow andcirculation through the nozzles 21, through the annular space vacated bybayonet contact 82, and in the plurality of oil pockets 60 and 78enhances the cooling effect and the arc is eventually extinguished.

As is apparent from the foregoing, withdrawal of bayonet 82 causesexposure of more and more oil pockets 60 and 78 and turbulence increasesas the arc elongates until it is extinguished.

' FIG. 3 shows an embodiment of the invention wherein an interruptingdevice 108 comprises external and internal structures 114 and 118,respectively, which are integrally formed and therefore provide a space180 which has a substantially C- shaped cross section and accommodates abayonet contact 182 which has a substantially C-shapedcross section.Device 108 comprises a cylindrical shell in which a stack of insulatingdisks, each having an exterior section 152 and an integrally formedinterior'section and an'opening 172. The openings 172 align to providethe space which accommodates bayonet contact 182. By providing a stackof disks which have openings 172 of different sizes, oil pockets such as160 and 178 are provided. Device 108 is similar to device 8 as regardsconstruction, components and operation except that no separatesupporting means such as rod 64 in device 8 are required. r

The embodiments'of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. An arc interrupting device for use in an oil-type circuit interrupterand adapted for electrical and mechanical connection to an electricallyconductive contact member, said device comprising:

a hollow insulating shell. having one end adapted for mechanicalconnection to said member,

said shell having at least one nozzle opening in the wall thereof,

stationary contact means mounted in said shell near said one end thereofand adapted for electrical connection to said member,

a plurality of stacked insulating disks in said shell providing anexternal insulating structure and an internal insulating structurebetween which a space is defined for accommodating passage of a hollowbayonet-type contact,

some of said disks having different configurations than others so as toprovide oil turbulence pockets on the interior of said externalstructure and on the exterior of said internal structure, A

the disks located adjacent said nozzle opening being provided withopenings which communicate between said nozzle opening'and said space,

- means at the other end of said shell for supporting said plurality ofdisks in said shell,

and a hollow bayonet-type contact for cooperative engagement with saidstationary contact means and movable in said space and surrounding atleast a portion of said internal structure.

2. A device accordingto claim 1 wherein said plurality of stackedinsulating disks comprises a first set of stacked disks which providessaid external insulating structure and a second set of stacked diskswhich provides said internal insulating structure, wherein said hollowbayonet-type contact is cylindrical in cross section, and wherein saidmeans for supporting said plurality of disks comprises a closure memberengaging said shell for holding said first set of disks in place andfurther comprises an insulated support member mechanically connected tosaid contact member and on which said second set of disks are mounted,

said insulated support member having a threaded end on which anonconductive nut is mounted. I

3. A device according to claim 1 wherein said'plurality of stackedinsulating disks comprises disks which have a substantially C-shapedopening therein, wherein said openings align to provide said space forsaid contact and said oil turbulence pockets, wherein said hollowbayonet-type contact is C- shaped in cross section, and wherein saidmeans for supporting said plurality of disks comprises a closure memberengaging said shell.

4. A device according to claim 2 wherein said closure member isexternally threaded and engages a threaded insert in said shell.

5. A device according to claim 3 wherein said closure member isexternally threaded and engages a threaded insert in said shell.

1. An arc interrupting device for use in an oil-type circuit interrupterand adapted for electrical and mechanical connection to an electricallyconductive contact member, said device comprising: a hollow insulatingshell having one end adapted for mechanical connection to said member,said shell having at least one nozzle opening in the wall thereof,stationary contact means mounted in said shell near said one end thereofand adapted for electrical connection to said member, a plurality ofstacked insulating disks in said shell providing an external insulatingstructure and an internal insulating structure between which a space isdefined for accommodating passage of a hollow bayonet-type contact, someof said disks having different configurations than others so as toprovide oil turbulence pockets on the interior of said externalstructure and on the exterior of said internal structure, the diskslocated adjacent said nozzle opening being provided with openings whichcommunicate between said nozzle opening and said space, means at theother end of said shell for supporting said plurality of disks in saidshell, and a hollow bayonet-type contact for cooperative engagement withsaid stationary contact means and movable in said space and surroundingat least a portion of said internal structure.
 2. A device according toclaim 1 wherein said plurality of stacked insulating disks comprises afirst set of stacked disks which provides said external insulatingstructure and a second set of stacked disks which provides said internalinsulating structure, wherein said hollow bayonet-type contact iscylindrical in cross section, and wherein said means for supporting saidplurality of disks comprises a closure member engaging said shell forhoLding said first set of disks in place and further comprises aninsulated support member mechanically connected to said contact memberand on which said second set of disks are mounted, said insulatedsupport member having a threaded end on which a nonconductive nut ismounted.
 3. A device according to claim 1 wherein said plurality ofstacked insulating disks comprises disks which have a substantiallyC-shaped opening therein, wherein said openings align to provide saidspace for said contact and said oil turbulence pockets, wherein saidhollow bayonet-type contact is C-shaped in cross section, and whereinsaid means for supporting said plurality of disks comprises a closuremember engaging said shell.
 4. A device according to claim 2 whereinsaid closure member is externally threaded and engages a threaded insertin said shell.
 5. A device according to claim 3 wherein said closuremember is externally threaded and engages a threaded insert in saidshell.